Lipase-catalyzed acidolysis of algal oils with a medium-chain fatty acid, capric acid

• Main Author: Hamam, Fayez
• Format: Thesis
• Language: English
• Published: Memorial University of Newfoundland 2003
• Subjects: Rugosa; Antarc*; Antarctica
• Online Access: https://research.library.mun.ca/6981/; https://research.library.mun.ca/6981/1/Hamam_Fayez.pdf; https://research.library.mun.ca/6981/3/Hamam_Fayez.pdf

Lipase-assisted acidolysis of algal oils with a medium-chain fatty acid (capric acid) was studied. Five commercially available lipase preparations from Candida antarctica, Mucor miehei, Pseudomonas sp., Aspergillus niger and Candida rugosa were initially used as biocatalysts for the incorporation of capric acid (CA) into selected algal oils. The algal oils of interest were arachidoinc acid single cell oil (ARASCO), docosahexaenoic acid single cell oil (DHASCO) and single cell oil rich in docosahexaenoic acid (DHA) and docosapentaenoic acid (DP A) (OMEGA-GOLD). Among the lipases examined, Pseudomonas sp. was the most efficient. -- Effects of various reaction variables, namely the mole ratio of substrates, enzyme amount, time course, temperature and the amount of added water were examined for Pseudomonas sp. Response surface methodology was used to obtain a maximum incorporation of CA into algal oils. The process variables studied were the amount of enzyme (2-12 %), reaction temperature (25-55°C) and incubation time (12-48h). All experiments were conducted according to a face-centred cube design. Under optimum conditions (12.3 % of enzyme; 45°C; 29.4 h), the incorporation of CA was 20.0 % into ARASCO. Optimization of acidolysis of DHASCO with CA gave rise to a maximum of 22.6 % at 4.2 % enzyme amount, and a reaction temperature of 43.3°C and reaction time of 27.1 h. Similarly, the maximum incorporation of CA into the OMEGA-GOLD oil was obtained when enzyme amounts, reaction temperature and time were 2.5 %, 46.6°C and 25.2 h, respectively. -- Stereospecific analysis was performed to establish positional distribution of fatty acids on the glycerol backbone of modified ARASCO, DHASCO and the OMEGA-GOLD oil. In all oils examined CA was mainly located at the sn-1 and sn-3 positions of the triacylglycerol (TAG) molecules. In ARASCO-based SL, arachidonic acid (ARA) was mostly esterified at the sn-2 position of the glycerol backbone. In DHASCO-based SL, DHA was concentrated in the sn-2 position, but also present in the ...